The free agency period for NFL players begins on March 13 at 3 p.m., and the Cowboys won't try or be able to re-sign all 16 of their free agents -- 14 unrestricted, plus one restricted and one exclusive rights. Here is the second installment this week counting down the five unrestricted free agents who are most likely to depart in 2019:

No. 4 -- OT Cameron Fleming

2018 impact: Fleming proved to be valuable insurance for the Cowboys at tackle, filling in for All-Pro left tackle Tyron Smith in three starts. The first came against the Washington Redskins on Thanksgiving, and Fleming didn't know until pregame warm-ups that Smith would be unable to play because of a neck stinger.

The former New England Patriot signed a one-year deal with the Cowboys last March. The franchise had learned how devastating not having a solid backup could be when Smith dealt with an array of injuries during the 2017 season.

Why Fleming is unlikely to return: Fleming could find a landing spot where he's better compensated and returns to a starting role, which is unlikely here. When he came to Dallas, it was with the idea that he could possibly start at right tackle, but the Cowboys kept La'el Collins at the position and drafted Connor Williams to play left guard. Fleming played in less than 22 percent of the offensive snaps in 2018. If he does leave, the Cowboys will again have to solidify their depth at tackle. Smith has missed at least three games each of the last three seasons.

Cowboys could address tight end or safety with their first 2019 draft pick, but these 2 positions may be bigger needs